In various forms of electronic equipment, e.g. a legacy shelf, signals are communicated between a common card and a plurality of line cards over a bus. The legacy shelf can be found in communication systems providing both POTS and DSL services. One such system is the CNX-5 Broadband DSL system. This system DSL enables Lucent SLC® Series 5 (SLC-5) Digital Loop Carriers. This system allows a service provider to deliver both POTS and DSL services on any copper pair without compromising POTS density.
In the SLC-5, the legacy shelf utilizes six (6) copper single ended wires of the existing ten (10) wire metallic test bus to create a 66 MPS capacity bus by dedicating four (4) of the six (6) wires to downstream traffic from a common card to a plurality of line cards and two (2) of the six (6) wires to upstream traffic from the line cards to the common card. A schematic of a legacy shelf is depicted in FIG. 1. The legacy shelf or dual channel bank includes bank A having forty-eight (48) line cards and bank B having forty-eight (48) line cards. Wires A1 through A6 connect the line cards in bank A to a common card C. Similarly, Wires B1 through B6 connect the line cards in bank B to the common card C. The line cards in each bank receive the signals with respect to ground.
With a legacy shelf having wires dedicated to traffic in only one direction, it is not possible to readily deploy advanced new communications products to deliver data transmissions at higher speeds than the system was originally designed to accommodate. For example, dedicating certain wires of the bus to either downstream traffic or upstream traffic limits the efficiency of the system when there is either no current downstream or upstream traffic. Another example of the limitations of previously configured legacy shelves is the cross talk that must be treated as high level noise stemming from the simultaneous transmission of downstream and upstream traffic over two or more of the group of wires. Crosstalk increases with the signal frequency, so the data baud rate is limited due to degradation of signal to noise.
Accordingly, there is a need for an apparatus and method to overcome these and other disadvantages of exiting systems.